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FAILED: patch "[PATCH] io_uring: convert io_buffer_idr to XArray" failed to apply to 5.11-stable tree

PATCH [email protected] 1 participant 1 message Mar 20, 2021

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The patch below does not apply to the 5.11-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9e15c3a0ced5a61f320b989072c24983cb1620c1 Mon Sep 17 00:00:00 2001
From: Jens Axboe <[email protected]>
Date: Sat, 13 Mar 2021 12:29:43 -0700
Subject: [PATCH] io_uring: convert io_buffer_idr to XArray

Like we did for the personality idr, convert the IO buffer idr to use XArray. This avoids a use-after-free on removal of entries, since idr doesn't like doing so from inside an iterator, and it nicely reduces the amount of code we need to support this feature.

Fixes 5a2e745d4d43 ("io_uring: buffer registration infrastructure")
Cc Matthew Wilcox <[email protected]>
Cc yangerkun <[email protected]>
fs/io_uring.c +15 -28
index 05adc4887ef3..58d62dd9f8e4 100644
@@ -402,7 +402,7 @@ struct io_ring_ctx {
 	struct socket		*ring_sock;
 #endif
 
-	struct idr		io_buffer_idr;
+	struct xarray		io_buffers;
 
 	struct xarray		personalities;
 	u32			pers_next;
@@ -1135,7 +1135,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	init_waitqueue_head(&ctx->cq_wait);
 	INIT_LIST_HEAD(&ctx->cq_overflow_list);
 	init_completion(&ctx->ref_comp);
-	idr_init(&ctx->io_buffer_idr);
+	xa_init_flags(&ctx->io_buffers, XA_FLAGS_ALLOC1);
 	xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
 	mutex_init(&ctx->uring_lock);
 	init_waitqueue_head(&ctx->wait);
@@ -2843,7 +2843,7 @@ static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
 
 	lockdep_assert_held(&req->ctx->uring_lock);
 
-	head = idr_find(&req->ctx->io_buffer_idr, bgid);
+	head = xa_load(&req->ctx->io_buffers, bgid);
 	if (head) {
 		if (!list_empty(&head->list)) {
 			kbuf = list_last_entry(&head->list, struct io_buffer,
@@ -2851,7 +2851,7 @@ static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
 			list_del(&kbuf->list);
 		} else {
 			kbuf = head;
-			idr_remove(&req->ctx->io_buffer_idr, bgid);
+			xa_erase(&req->ctx->io_buffers, bgid);
 		}
 		if (*len > kbuf->len)
 			*len = kbuf->len;
@@ -3892,7 +3892,7 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx, struct io_buffer *buf,
 	}
 	i++;
 	kfree(buf);
-	idr_remove(&ctx->io_buffer_idr, bgid);
+	xa_erase(&ctx->io_buffers, bgid);
 
 	return i;
 }
@@ -3910,7 +3910,7 @@ static int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
 	lockdep_assert_held(&ctx->uring_lock);
 
 	ret = -ENOENT;
-	head = idr_find(&ctx->io_buffer_idr, p->bgid);
+	head = xa_load(&ctx->io_buffers, p->bgid);
 	if (head)
 		ret = __io_remove_buffers(ctx, head, p->bgid, p->nbufs);
 	if (ret < 0)
@@ -3993,21 +3993,14 @@ static int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
 
 	lockdep_assert_held(&ctx->uring_lock);
 
-	list = head = idr_find(&ctx->io_buffer_idr, p->bgid);
+	list = head = xa_load(&ctx->io_buffers, p->bgid);
 
 	ret = io_add_buffers(p, &head);
-	if (ret < 0)
-		goto out;
-
-	if (!list) {
-		ret = idr_alloc(&ctx->io_buffer_idr, head, p->bgid, p->bgid + 1,
-					GFP_KERNEL);
-		if (ret < 0) {
+	if (ret >= 0 && !list) {
+		ret = xa_insert(&ctx->io_buffers, p->bgid, head, GFP_KERNEL);
+		if (ret < 0)
 			__io_remove_buffers(ctx, head, p->bgid, -1U);
-			goto out;
-		}
 	}
-out:
 	if (ret < 0)
 		req_set_fail_links(req);
 
@@ -8333,19 +8326,13 @@ static int io_eventfd_unregister(struct io_ring_ctx *ctx)
 	return -ENXIO;
 }
 
-static int __io_destroy_buffers(int id, void *p, void *data)
-{
-	struct io_ring_ctx *ctx = data;
-	struct io_buffer *buf = p;
-
-	__io_remove_buffers(ctx, buf, id, -1U);
-	return 0;
-}
-
 static void io_destroy_buffers(struct io_ring_ctx *ctx)
 {
-	idr_for_each(&ctx->io_buffer_idr, __io_destroy_buffers, ctx);
-	idr_destroy(&ctx->io_buffer_idr);
+	struct io_buffer *buf;
+	unsigned long index;
+
+	xa_for_each(&ctx->io_buffers, index, buf)
+		__io_remove_buffers(ctx, buf, index, -1U);
 }
 
 static void io_req_cache_free(struct list_head *list, struct task_struct *tsk)